Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/24/2002
Publication Date: N/A
Interpretive Summary: Some early investigations and field observations by producers have led some people to believe that herbicide applications may influence the severity of diseases associated with soybean. We designed and conducted experiments involving several modern soybean cultivars and a variety of preemergence and postemergence herbicides, over several environmental conditions, to assess the effect of these variables on the quality of harvested soybean seed. Several different herbicides were applied to a variety of soybean cultivars at four locations in Illinois between 1997 and 2000. Soybean seeds were harvested at maturity and evaluated for seed quality parameters. Percentage of the seeds that were infected with Phomopsis spp. ranged from 1 to 40%, whereas percentage of seeds infected with Cercospora kikuchii was lower, and ranged from 0 to 4% in these investigations. We found that the herbicides used in these studies have little or no effect on seed quality parameters such as incidence of seed pathogens and percent germination. Also, herbicides used did not affect the concentration of oil or protein in the harvested seeds. Soybean seed quality was affected by Phomopsis spp. in that as the percentage of infected seed increased, % germination was decreased. In these investigations over several environments, it appears that Phomopsis spp. may be a more prevalent seed pathogen than is Cercospora kikuchii for soybean fields in central and northern Illinois. These findings have helped to clarify that modern herbicides on modern soybean cultivars have little to no effect on soybean seed pathogens or oil or protein content. The results should be beneficial to researchers and public and private outreach personnel who are conducting soybean pest management research and preparing guidelines for soybean production and protection.
Technical Abstract: Different herbicides were applied to soybean plants in field plots planted to different soybean cultivars located at four locations in Illinois between 1997 and 2000. Treatments varied from hand weeded to preemergence herbicides to postemergence herbicides. Soybean seeds were harvested and evaluated for different seed quality parameters. The percentage of seeds infected with Phomopsis spp. ranged from 1 to 40%, and the percentage of seeds infected with Cercospora kikuchii was low, ranging from 0 to 4%. Herbicides had little or no effect on seed quality parameters such as percent germination and incidence of seed pathogens or on protein and oil concentrations. Soybean seed quality was affected by Phomopsis spp. In that there were significant(P 0.05)inverse correlations between Phomopsis spp. Incidence and percentage see germination. It appears that Phomopsis spp. may be a more prevalent seed pathogen than C. kikuchii for soybean fields in central to northern Illinois.